Opportunity Rover Finds Intriguing New Spherules at Cape York

Mosaic image of the spherules in the rock outcrop on Cape York at Endeavour crater. Credit: NASA / JPL-Caltech / Stuart Atkinson

One of the most interesting discoveries made so far by the Opportunity rover on Mars has been the small round spherules or “blueberries” as they are commonly referred to, covering the ground at the rover’s landing site. Typically only a few millimetres across, some lie loose on the soil while others are imbedded in rock outcrops.

Analysis by Opportunity indicates that they are most likely a type of concretion, which are also found on Earth. These Martian concretions have been found to contain the mineral hematite, which explains its detection in this region from orbit, and one of the main reasons that the rover was sent to this location in Meridiani Planum in the first place. They are similar to the Moqui Marbles, iron-oxide concretions in the outcrops of Navajo Sanstone in Utah, which formed in groundwater.

Now, the rover (eight years later and still going!) has found what may be a different type of spherule. These ones generally resemble the previous ones, but are quite densely packed in an unusual rock outcrop that is on the eastern side of Cape York, the small island-like ledge on the rim of the huge Endeavour crater. With brittle-looking “fins” of material, the outcrop is an an area that from orbit has been identified as containing small clay deposits. There are also more substantial clay deposits farther south along Endeavour’s rim at the much larger Cape Tribulation, the next major destination of Opportunity.

Whether this outcrop actually has any clay in it isn’t known yet, but the examination of it by Opportunity continues at the time of this writing. Some spherules have apparently broken off the outcrop, exposing their inside structure. The new close-up images of the spherules were taken by the Microscopic Imager (MI) on the rover.

A portion of the rock outcrop. Credit: NASA / JPL-Caltech / Stuart Atkinson

What makes these spherules of interest is the possibility that they may be connected somehow to the clay deposits. Their dense concentration in the outcrop and the physical nature of the outcrop itself may indicate a different origin than the other spherules seen previously, as well as the fact that no hematite signature has been seen from orbit in this specific area (although there may be smaller amounts of hematite here as well). We will just have to wait for the results of the rover’s analysis to come back, but they should be interesting.

Opportunity is specifically looking for the clay deposits in this area, as they could have formed in non-acidic (or pH neutral) water as often happens on Earth. As we have seen in just the last few days though, the origin of Martian clays is itself still a subject of debate.

The whitish gypsum veins already seen at Cape York and examined by Opportunity also indicate the presence of liquid water at this location in the distant past. There are some interesting light-coloured veins in this same outcrop as well; whether they are also gypsum or something else isn’t known yet.

Thanks also to Stuart Atkinson for his excellent mosaic images made from the original Opportunity photos.

New Analysis of Clay Deposits in Ancient Martian Lakes

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Mars was once a much wetter world than it is now, with hot springs, rivers, lakes and perhaps even oceans. Just how wet exactly, and for how long, is still a subject of considerable debate. One vital clue comes from clay mineral deposits and sediments left over after the water disappeared, but still visible now. They provide a valuable insight into what Mars used to be like, and why it is the cold, dry place we see today.

A team of scientists from Brown University has just completed a new study of ancient lake beds on Mars, specifically looking at the clay deposits within them, to try to determine how many of these lakes still contain such deposits and their composition. So what do they tell us about conditions on early Mars? How does this affect the search for evidence of life?

As it turns out, about a third of the lake beds examined still show evidence for clay deposits. A total of 79 lake beds out of 226 studied to be exact, indicating that they are less common on Mars than on Earth. The reason for this may be that the chemistry of the water was not ideal for preserving clays or that the lakes were relatively short-lived.

The paper was just published in Icarus on March 2, 2012.

From the abstract:

“These results indicate that hydrated and evaporite minerals are not as commonly associated with lacustrine deposits on Mars as they are on Earth. This suggests in situ alteration and mineral precipitation, a common source of such minerals in terrestrial lakes, was not a major process occurring in these paleolacustrine systems, and that the observed minerals are likely to be present as transported material within the lacustrine deposits. The lack of widespread in situ alteration also suggests that either the water chemistry in these paleolake systems was not conducive to aqueous alteration and mineral precipitation, or that the open-basin lake systems were relatively short-lived.”

Images for the study came from the Mars Reconnaissance Orbiter, Mars Odyssey and Mars Express spacecraft.

Clay deposits have become a primary focus of study by orbiters and rovers, as they could preserve fossil traces of early life, just as they do on Earth. Even if they are less common on Mars, the fact that they do exist there is exciting, and there is now much interest in exploring them further. Apart from underground, they are the best places to look for such evidence of life. It is also possible that additional deposits have been buried underground, waiting to be discovered.

The Opportunity rover is currently very close to a treasure trove of clays in Endeavour crater, and it is expected to head straight for them after its winter “hibernation” is over in the next few months. The Curiosity rover, en route to Mars right now, will land in Gale crater next July, where there are also clay deposits near the base of a mountainous peak within the crater. Gale crater is thought to be another site of a former Martian lake.

The abstract is available here (with full paper available for purchase).

Does Mars Still Shake, Rattle and Roll?

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Compared to Earth, Mars is a relatively quiet planet, geologically speaking. Actually, very quiet, as in pretty much dead. While it has volcanoes much larger than any here, they have been inactive for a very long time; the latest studies suggest however that volcanic activity may have continued until only a matter of millions of years ago. That seems like an eternity to our human sense of time, but geologically, it is quite recent.

There is also the massive canyon system Valles Marineris, much larger than the Grand Canyon here on Earth, and evidence for ancient hot springs, glaciers, etc. which also show that Mars was once much more active than it is today.

Now, there is also evidence that marsquakes (as in earthquakes here) continued to shake the planet until only a few million years ago, and may even still happen today.

Earthquakes are a common, daily occurrence on our planet, but what about Mars? If they do still happen, they would seem to be much more infrequent than they are here. The new study, however, supports the idea that Mars was geologically active for longer than previously thought, and perhaps still is.

Scientists in Europe have been examining images of a Martian fault system, Cerberus Fossae, taken by the Mars Reconnaissance Orbiter. They’ve found a spot where boulders have tumbled down cliffs near the fault; what’s interesting is that they are primarily found in one location, best explained by marsquakes rather than melting ice and avalanches. This grouping of boulders suggests that they were near the epicentre of a marsquake. The trails behind the rolling boulders are still visible, indicating that they must have fallen relatively recently, with not enough time yet for winds to erase the trails.

Closeup of boulders and trails in Cerberus Fossae. Credit: NASA/JPL/University of Arizona

Marsquakes would also be evidence for possible continued volcanism on the planet, even if only deep underground. That itself has further implications, since it is already known that there are massive ice deposits beneath the surface, even closer to the equator. Heat from any recent or current activity could create liquid water in places, which of course leads back to the question of possible present or past life.

Falling boulders, then, while an interesting observation in themselves, may actually also help to solve some of the ongoing mysteries about the Red Planet.

The study was published in the Journal of Geophysical Research. The paper is available here (by subscription or for $25.00 US).

Exciting New ‘Enceladus Explorer’ Mission Proposed to Search for Life


Water vapour geysers erupting from Enceladus' south pole. Credit: NASA/JPL

Along with Jupiter’s moon Europa, a tiny Saturnian moon, Enceladus, has become one of the most fascinating places in the solar system and a prime target in the search for extraterrestrial life. Its outward appearance is that of a small, frozen orb, but it revealed some surprises when the Cassini spacecraft gave us our first ever close-up look at this little world – huge geysers of water vapour spewing from its south pole. The implications were thought-provoking: Enceladus, like Europa, may have an ocean of liquid water below the surface. Unlike Europa however, the water is apparently able to make it up to the surface via fissures, erupting out into space as giant plumes.

Now, a new project sponsored by the German Aerospace Center, Enceladus Explorer, was launched on February 22, 2012, in an attempt to answer the question of whether there could be life on (or rather, inside) Enceladus. The project lays the groundwork for a new, ambitious mission being proposed for some time in the future.

Cassini was able to sample some of the plumes directly during its closest approaches to the moon, revealing that they contain water vapour, ice particles and organic molecules. If they originate from a reservoir of subsurface liquid water, as now thought by most scientists involved, it would indicate an environment which could be ideal for life to have started. The necessary ingredients for life (as we know it at least) are all there – water, heat and organic material. The fissures themselves generate much more heat relatively than the surrounding surface, suggesting that the conditions below the surface are much warmer. Maybe not “hot” per se, but warm enough, perhaps also with the aid of salts like in Earth’s oceans, to keep the water liquid.

But what is the best way to search for evidence of life there?  Follow-up missions have been proposed, to again sample the plumes, but with instruments able to look for life itself, which Cassini can’t do. This would seem ideal, as the water is being spewed out into space, with no drilling through the ice necessary. But the Enceladus Explorer project is proposing to do just that; the rationale is that any organisms (most likely microscopic) which may be in the water could easily be destroyed by the force of the ejection from the fissure. So then what is the best way to sample the water itself down below?

Enceladus Explorer would place a base station on the surface near one of the fissures; an ice drilling probe, the IceMole, would then melt its way through the ice crust to a depth of 100-200 metres until it reaches a liquid water reservoir. It would obtain samples of the water and examine them in situ for any traces of microorganisms. With no GPS system available, or external reference points to use, the probe would need to function autonomously, finding its own way through the ice to the water below.

The IceMole is already being tested here on Earth, and has successfully melted its way through the ice of the Morteratsch glacier in Switzerland. The next experiment will have it navigate its way through ice in the Antarctic, sampling completely uncontaminated water from a subsurface lake below the ice, much like the conditions found on Enceladus.

There is no timeframe yet for such a mission, especially given current budgets, but the Enceladus Explorer project has already shown that it is certainly technologically feasible and would provide an incredible look at an environment in the outer solar system which is amazingly Earth-like yet utterly alien at the same time.

35 Years Later, the ‘Wow!’ Signal Still Tantalizes

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Since the SETI program first began searching for possible alien radio signals a few decades ago, there have been many false alarms but also instances of fleeting signals of interest which disappeared again as quickly as they had appeared. If a potential signal doesn’t repeat itself so it can be more carefully observed, then it is virtually impossible to determine whether it is of truly cosmic origin. One such signal in particular caught astronomers’ interest on August 15, 1977. The famous “Wow!” signal was detected by the Big Ear Radio Observatory at Ohio State University; it was thirty times stronger than the background noise but lasted only 72 seconds and was never heard again despite repeated subsequent searches.

In a new book titled The Elusive Wow, amateur astronomer Robert Gray chronicles the quest for the answer to this enduring puzzle.

When the signal was first seen in the data, it was so pronounced that SETI scientist Jerry Ehman circled it on the computer printouts in red ink and wrote “Wow!” next to it. It appeared to fit the criteria for an extraterrestrial radio signal, but because it wasn’t heard again, the follow-up studies required to either confirm or deny this were not possible. So what was it about the signal that made it so interesting?

First, it did appear to be an artificial radio signal, rather than a natural radio emission such as a pulsar or quasar. The Big Ear telescope used a receiver with 50 radio channels; the signal was only heard on one frequency, with no other noise on any of the other channels. A natural emission would cause static to appear on all of the frequencies, and this was not the case. The signal was narrow and focused, as would be expected from an artificial source.

The Big Ear Radio Observatory. Credit: Big Ear Radio Observatory / North American AstroPhysical Observatory / Ohio State University

The signal also “rose and fell” during the 72 seconds, as would be expected from something originating in space. When the radio telescope is pointed at the sky, any such signal will appear to increase in intensity as it first moves across the observational beam of the telescope, then peak when the telescope is pointed straight at it and then decrease as it moves away from the telescope. This also makes a mere computer glitch a less likely explanation, although not impossible.

What about satellites? This would seem to be an obvious possible explanation, but as Gray notes, a satellite would have to be moving at just the right distance and at just the right speed, to mimic an alien signal. But then why wasn’t it observed again? An orbiting satellite will broadcast its signal repeatedly. The signal was observed near the 1420 MHz frequency, a “protected spectrum” in which terrestrial transmitters are forbidden to transmit as it is reserved for astronomical purposes.

There may be a bias in thinking that any alien signals will be like ours which leak out to space continuously, ie. all of our radio and TV broadcasts. That is, “normal” radio emissions from every-day type technologies which could easily be seen on an ongoing basis. But what if they were something more like beacons, sent out intentionally but only on a periodic basis? As Gray explains, radio searches to date have tended to look at many different spots in the sky, but they will only examine any particular spot for a few minutes or so before moving on to the next. A periodic signal could easily be missed completely, or if seen, it may be a long time before it is seen again.

Of course, it is also possible that any other civilizations out there might not even use radio at all, especially if they are more advanced than us (while other intelligent life might be behind us, as well). A newer branch of SETI is now searching for artificial sources of light, like laser beams, used as beacons.

So where does this leave us? The “Wow!” signal still hasn’t been adequately explained, although various theories have been proposed over the years. Perhaps one day it will be observed again, or another one like it, and we will be able to solve the mystery. Until then, it remains a curiosity, a tantalizing hint of what a definite signal from an extraterrestrial civilization might look like.

More information is available at the Big Ear Radio Observatory website.

‘Stealth Merger’ of Dwarf Galaxies Seen in New Images

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Space may be vast, but accidents can still happen, like when galaxies “collide,” usually resulting in the smaller one having its stars scattered by the larger one. New high-resolution images of two dwarf galaxies merging together have now been obtained by astronomers, providing a more detailed look at something which could only barely be seen before. While the larger galaxy of the two, NGC 4449, is easily visible, its smaller companion was little more than just a faint smudge until now.

The new study comes from an international team of astronomers led by David Martínez-Delgado of the Max Planck Institute for Astronomy in Heidelberg. Their paper will be published in an upcoming issue of Astrophysical Journal Letters.

When the galaxies collide, the smaller one essentially gets torn apart by the larger one. As explained by Aaron Romanowsky, an astronomer at the University of California, Santa Cruz (UCSC), “This is how galaxies grow. You can see the smaller galaxy coming in and getting shredded, eventually leaving its stars scattered through the halo of the host galaxy.”

The remains of the smaller galaxy appear as a dense stream of stars in the outer regions of the larger one. It was initially seen as just a faint smudge in digitized photographic plates from the Digitized Sky Survey project. Because this smaller galaxy, or what’s left of it, is so difficult to see, the merging process has been referred to as a “stealth merger.”

The new images, taken by the Black Bird Observatory and Subaru Telescope, show the merger in such detail that individual stars can be seen. “I don’t think I’d ever seen a picture of a galaxy merger where you can see the individual stars. It’s really an impressive image,” said Romanowsky.

NGC 4449 is about 12.5 million light-years from Earth and is part of a group of galaxies found in the constellation Canes Venatici. It is similar to one of our own Milky Way’s satellite galaxies, the Large Magellanic Cloud.

While larger galaxies merging with other large galaxies are commonly seen, it has been more difficult to find examples of smaller galaxies doing the same thing. Romanowsky continues: “We should see the same things at smaller scales, with small galaxies eating smaller ones and so on. Now we have this beautiful image of a dwarf galaxy consuming a smaller dwarf.”

In addition, the companion galaxy was also independently discovered by astronomers at the University of California, Los Angeles (UCLA). Their own paper will be published in the February 9, 2012  issue of Nature.

The paper is available here. See also the Subaru Telescope press release here.

Scientists Find New Clues About the Interiors of ‘Super-Earth’ Exoplanets

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As we learned in science class in school, the Earth has a molten interior (the outer core) deep beneath its mantle and crust. The temperatures and pressures are increasingly extreme, the farther down you go. The liquid magmas can “melt” into different types, a process referred to as pressure-induced liquid-liquid phase separation. Graphite can turn into diamond under similar extreme pressures. Now, new research is showing that a similar process could take place inside “Super-Earth” exoplanets, rocky worlds larger than Earth, where a molten magnesium silicate interior would likely be transformed into a denser state as well.

Simply put, the magnesium silicate undergoes what’s called a phase change while in the liquid state. The scientists were able to replicate the extreme temperatures and pressures that would be found inside those exoplanets by using the Janus laser at the Lawrence Livermore National Laboratory and OMEGA at the University of Rochester. A powerful laser pulse generated a shock wave as it passed through the samples. Changes in the velocity of the shock and the temperature of the sample indicated when a phase change was detected.

Interestingly, the different liquid states of the silicate magma in the experiments showed different physical properties under high pressures and temperatures, even though they were still of the same composition. Due to varying densities, the different liquid states tended to want to separate, much like oil and water.

The findings should help to better understand the interiors of terrestrial-type exoplanets, whether they are “Super-Earths” or smaller, like Earth or Mars.

Lead scientist Dylan Spaulding, at the University of California, Berkeley, states: “Phase changes between different types of melts have not been taken into account in planetary evolution models. But they could have played an important role during Earth’s formation and may indicate that extra-solar ‘Super-Earth’ planets are structured differently from Earth.”

The paper was published in the February 10, 2012 edition of the journal Physical Review Letters.

Tidal Heating on Some Exoplanets May Leave Them Waterless

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As the number of exoplanets being discovered continues to increase dramatically, a growing number are now being found which orbit within their stars’ habitable zones. For smaller, rocky worlds, this makes it more likely that some of them could harbour life of some kind, as this is the region where temperatures (albeit depending on other factors as well) can allow liquid water to exist on their surfaces. But there is another factor which may prevent some of them from being habitable after all – tidal heating, caused by the gravitational pull of one star, planet or moon on another; this effect which creates tides on Earth’s oceans can also create heat inside a planet or moon.

The findings were presented at the January 11 annual meeting of the American Astronomical Society in Austin, Texas.

The habitability factor is determined primarily by the amount of heat coming from the planet’s star. The closer a planet is to its star, the hotter it will be, and the farther out it is, the cooler it will be. Simple enough, but tidal heating adds a new wrinkle to the equation. According to Rory Barnes, a planetary scientist and astrobiologist at the University of Washington, “This has fundamentally changed the concept of a habitable zone. We figured out you can actually limit a planet’s habitability with an energy source other than starlight.”

This effect could cause planets to become “tidal Venuses.” In these cases, the planets orbit smaller, dimmer stars, where in order to be in that star’s habitable zone, they would need to orbit much closer in to the star than Earth does with the Sun. The planets would then be subjected to greater tidal heating from the star, enough perhaps to cause them to lose all of their water, similar to what is thought to have happened with Venus in our own solar system (ie. a runaway greenhouse effect). So even though they are within the habitable zone, they would lack oceans or lakes.

What’s problematic is that these planets could subsequently actually have their orbits altered by the tidal heating so that they are no longer affected by it. They would then be more difficult to distinguish from other planets in those solar systems which may still be habitable. While technically still within the habitable zone, they would have effectively been sterilized by the tidal heating process.

Planetary scientist Norman Sleep at Stanford University adds: “We’ll have to be careful when assessing objects that are very near dim stars, where the tides are much stronger than we feel on present-day Earth. Even Venus now is not substantially heated by tides, and neither is Mercury.”

In some cases, tidal heating can be a good thing though. The tidal forces exerted by Jupiter on its moon Europa, for example, are thought to create enough heat to allow a liquid water ocean to exist beneath its outer ice crust. The same may be true for Saturn’s moon Enceladus. This makes these moons still potentially habitable even though they are far outside of the habitable zone around the Sun.

By design, the first exoplanets being found by Kepler are those that orbit closer in to their stars as they are easier to detect. This includes smaller, dimmer stars as well as ones more like our own Sun. The new findings, however, mean that more work will need to be done to determine which ones really are life-friendly and which ones are not, at least for “life-as-we-know-it” anyway.

New Computer Simulations Show Earth’s Spaghetti-Like Magnetosphere

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A new computer simulation is showing Earth’s magnetosphere in amazing detail – and it looks a lot like a huge pile of tangled spaghetti (with the Earth as a meatball). Or perhaps a cosmic version of modern art.

The magnetosphere is formed by the Sun’s magnetic field interacting with Earth’s own magnetic field. When charged particles from a solar storm, also known as a coronal mass ejection (CME), impact our magnetic field, the results can be spectacular, from powerful electrical currents in the atmosphere to beautiful aurorae at high altitudes. Space physicists are using the new simulations to better understand the nature of our magnetosphere and what happens when it becomes extremely tangled.

Using a Cray XT5 Jaguar supercomputer, the physicists can better predict the effects of space weather, such as solar storms, before they actually hit our planet. According to Homa Karimabadi, a space physicist at the University of California-San Diego (UCSD), “When a storm goes off on the sun, we can’t really predict the extent of damage that it will cause here on Earth. It is critical that we develop this predictive capability.” He adds: “With petascale computing we can now perform 3D global particle simulations of the magnetosphere that treat the ions as particles, but the electrons are kept as a fluid. It is now possible to address these problems at a resolution that was well out of reach until recently.”

It helps that the radiation from solar storms can take 1-5 days to reach Earth, providing some lead time to assess the impact and any potential damage.

The previous studies were done using the Cray XT5 system known as Kraken; with the new Cray XT5 Jaguar supercomputer, they can perform simulations three times as large. The earlier simulations contained a “resolution” of about 1 billion individual particles, while the new ones contain about 3.2 trillion, a major improvement.

So next time you are eating that big plate of spaghetti, look up – the universe has its own recipes as well.

The original press release from Oak Ridge National Laboratory is here.

Do Alien Civilizations Inevitably ‘Go Green’?

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In the famous words of Arthur C. Clarke, “Any sufficiently advanced technology is indistinguishable from magic.” This phrase is often quoted to express the idea that an alien civilization which may be thousands or millions of years older than us would have technology so far ahead of ours that to us it would appear to be “magic.”

Now, a variation of that thought has come from Canadian science fiction writer Karl Schroeder, who posits that “any sufficiently advanced technology is indistinguishable from nature.” The reasoning is that if a civilization manages to exist that long, it would inevitably “go green” to such an extent that it would no longer leave any detectable waste products behind. Its artificial signatures would blend in with those of the natural universe, making it much more difficult to detect them by simply searching for artificial constructs versus natural ones.

The idea has been proposed as an explanation for why we haven’t found them yet, based on the premise that such advanced societies would have visited and colonized our entire galaxy by now (known as the Fermi Paradox). The question becomes more interesting in light of the fact that astronomers now estimate that there are billions of other planets in our galaxy alone. If a civilization reaches such a “balance with nature” as a natural progression, it may mean that traditional methods of searching for them, like SETI, will ultimately fail. Of course, it is possible, perhaps even likely, that civilizations much older than us would have advanced far beyond radio technology anyway. SETI itself is based on the assumption that some of them may still be using that technology. Another branch of SETI is searching for light pulses such as intentional beacons as opposed to radio signals.

But even other alternate searches, such as SETT (Search for Extraterrestrial Technology), may not pan out either, if this new scenario is correct. SETT looks for things like the spectral signature of nuclear fission waste being dumped into a star, or leaking tritium from alien fusion powerplants.

Another solution to the Fermi Paradox states that advanced civilizations will ultimately destroy themselves. Before they do though, they could have already sent out robotic probes to many places in the galaxy. If those probes were technologically savvy enough to self-replicate, they could have spread themselves widely across the cosmos. If there were any in our solar system, we could conceivably find them. Yet this idea could also come back around to the new hypothesis – if these probes were advanced enough to be truly “green” and not leave any environmental traces, they might be a lot harder to find, blending in with natural objects in the solar system.

It’s an intriguing new take on an old question. It can also be taken as a lesson – if we can learn to survive our own technological advances long enough, we can ultimately become more of a green civilization ourselves, co-existing comfortably with the natural universe around us.